Managing Glance images

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Find out how to import, verify, share and delete images in Glance on SNC Cloud Platform, and create volumes from them with the OpenStack CLI

Objective

Practical guide to importing, verifying and managing images in Glance (OpenStack's image catalogue service) on SNC Cloud Platform. Target audience: anyone who needs an image not in the default catalogue.

This guide covers an image's full lifecycle in Glance on this platform: import, verification, use for creating a volume or instance, visibility management, deletion — with the specifics of this platform, which complement generic OpenStack documentation.

Requirements

The openstack CLI configured (see the Terraform guide for clouds.yaml-based authentication).
The member role, at minimum.
A local machine with enough free disk space to stage the image being imported — the upload happens from the local machine, not server-side (see the "Available import methods" section).

Instructions

Available import methods

Glance offers several import methods. On this platform, only openstack image create --file (direct upload from the local machine) is supported — it is the recommended method:

Method	How it works	On this platform
`openstack image create --file` (direct upload, CLI)	The file is streamed from the local machine to Glance over HTTP	✅ Recommended method, used in this guide. A ~7-8 GB file typically imports in 1 to 3 minutes depending on the local machine's upload bandwidth.
`web_download`	Glance downloads the image server-side, from a supplied URL	❌ Not functional on this platform, due to the network segmentation requirements tied to the ongoing SecNumCloud qualification (internal services have no outbound Internet access) — prefer the direct upload above.
Manual upload via the Horizon UI	Uploading a local file through the "Create Image" web form	⚠️ Not working yet. Use the CLI (`openstack image create --file`), which is fully supported.
`copy-image`	Duplicates an image already present in Glance to another store	✅ Works (tested: `openstack image import <image> --method copy-image --store <store>`). Mainly useful in a multi-store context; this platform currently exposes a single store (`defaultstore`).

Step 1 — Listing existing images

Before importing anything, check whether an equivalent image already exists:

openstack image list -f table -c Name -c Status -c Visibility

Base catalogue generally available on this platform (varies by project): common Linux distributions (Debian, AlmaLinux, CentOS) as ready-to-use OVH images (cloud-init included). Any image outside this catalogue (Windows, an unlisted distribution, a specific appliance) needs to be imported manually.

Step 2 — Importing an image

openstack image create \
  --disk-format <format> \
  --container-format bare \
  --private \
  --progress \
  --file /local/path/to/image \
  image-name

Picking the right `--disk-format`

File type	`--disk-format`	Typical use
Install ISO (Windows, a Linux distribution's installer)	`iso`	Boot from a virtual CD-ROM to launch an interactive or automated installer
QCOW2 disk image (QEMU native format, often with cloud-init)	`qcow2`	Ready-to-use image, boots directly
RAW disk image	`raw`	Ready-to-use image, no compression

--container-format bare fits nearly every case (no extra container metadata needed).

--private restricts the image's visibility to your project (see step 5).

Importing a large image

--progress shows a progress bar during the upload — useful for multi-GB files, where several minutes without visible feedback might otherwise suggest a stalled upload.

Step 3 — Verifying an imported image

openstack image show image-name -f value -c status -c size -c checksum -c disk_format

status should read active. Any other value persisting (queued, saving) signals an import that is not progressing — see the "Known pitfalls (troubleshooting)" section.

Step 4 — Creating a volume from an image

Two use cases, with different behaviour observed in practice:

Standalone volume (recommended)

openstack volume create --image image-name --size <size-GB> volume-name

Works reliably and quickly (tens of seconds for several GB). Prefer this method to verify that an image converts correctly to a volume before using it to create an instance.

Warning

<size-GB> must be strictly greater than the image's virtual size (Glance's virtual_size), not its compressed size on disk. An image weighing a few hundred MB can have a virtual size of 15-20 GB once decompressed.

Volume created alongside an instance (`server create --block-device`)

openstack server create \
  --block-device uuid=<image-id>,source_type=image,destination_type=volume,volume_size=<size-GB> \
  ...

Warning

Good practice: creating multiple source_type=image block devices at once in a single server create call can leave the instance in task_state=scheduling/spawning for longer than expected before reaching ACTIVE. The recommended approach on this platform is to pre-create each volume separately (fast and reliable, method above), then reference them in server create with source_type=volume (not image):

openstack server create \
  --block-device uuid=<volume-id>,source_type=volume,destination_type=volume,boot_index=0 \
  ...

Step 5 — Managing an image's visibility

openstack image set --private image-name   # visible only to the current project
openstack image set --shared image-name    # explicit sharing with specific projects

# once shared, grant a specific project access to it:
openstack image add project image-name <target-project-id>

--private is the recommended default for an image imported for a one-off use (test, Windows VM). --shared works as expected on this platform to share an image with specific projects. public visibility (accessible to every project on the platform) is not available.

Step 6 — Deleting an image

openstack image delete image-name

An image cannot be deleted while a volume or instance still directly depends on it. Whether a dependency remains depends on the attachment method: a volume already created from the image no longer depends on it. Check for active usage before deleting:

openstack volume list --property image_id=<image-id> -f table

Known pitfalls (troubleshooting)

Symptom	Explanation	Recommendation
Import stuck in `queued` status, no progress	`web_download` attempted from an external URL — not a supported method on this platform (see available import methods)	Use direct upload from the local machine instead (`openstack image create --file`, step 2)
Horizon's "Create Image" form is not available	Not working yet on this platform	Use the CLI (`openstack image create --file`)
An import error's detail (`/v2/tasks/<id>`) is not directly viewable	The `/tasks` API is not exposed on this platform	Check the high-level status via `openstack image show`; for finer diagnostics, contact OVHcloud support
`Block Device <id> is not bootable` when creating an instance on a volume created from an image	Rare with a standard image (the `bootable` flag is normally set automatically by Cinder during an image→volume conversion) — mostly concerns blank volumes (`source_type=blank`), which are outside Glance's scope	See the Creating a Windows Server VM guide for the blank-volume case
Instance taking a while to reach `ACTIVE` with several `source_type=image` block devices in the same `server create` call	Converting several images to volumes simultaneously at boot time is not the recommended approach on this platform	Pre-create each volume separately via `openstack volume create --image`, then reference the volumes (`source_type=volume`) in `server create` — see step 4
`Image virtual size is XGB and doesn't fit in a volume of size YGB`	`--size`/`volume_size` smaller than the image's actual virtual size	Increase the size with a comfortable margin above the `virtual_size` reported by Glance

Go further

Creating a Windows Server VM — importing an ISO, full use case including blank volumes; same platform, same import limitations.

Terraform guide — the data "openstack_images_image_v2" pattern for reusing an existing image without recreating it.

Official OpenStack Image (Glance) CLI documentation: docs.openstack.org — Image v2.

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